Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
stack=deque()
c=[input() for i in range(H)]
ans=0
for ci in c:
    for j in ci:
        if j==".":
            ans+=1
reached=[[0]*W for i in range(H)]
stack.append((0,0))
dydx=[(1,0),(-1,0),(0,1),(0,-1)]
while(stack):
    Y,X=stack.popleft()
    for dy,dx in dydx:
        y=Y+dy
        x=X+dx
        if y<0 or y>=H or x<0 or x>=W or c[y][x]=="#":
            continue
        if reached[y][x]!=0:
            continue
        stack.append((y,x))
        reached[y][x]=reached[Y][X]+1
if reached[H-1][W-1]==0:
    print(-1)
else:
    print(ans-(reached[H-1][W-1]+1))